3.1 atoms and structure

Question 1

atom

Answer 1

smallest particle of an element that retains its identity in a chemical reaction

Question 2

democritus believed:

Answer 2

-atoms were indestructible (lacked experimental support)

Question 3

law of conservation of mass

Answer 3

in a chemical reaction, matter is neither created nor destroyed

Question 4

law of definite proportions

Answer 4

all samples of a given compound have the same proportions of their constituent elements

Question 5

law of multiple proportions

Answer 5

when 2 elements (A and B) form 2 different compounds, the masses of element B that combine with 1g of element A can be expressed as a ratio of small whole numbers

mass oxygen per 1g carbon in carbon dioxide 2.67
——————————————————————-=——-=2
mass oxygen per 1g carbon in carbon monoxide 1.33

Question 6

Dalton’s atomic theory

Answer 6

-used experimental methods to transform Democritus’s ideas into a theory
-all elements are composed of tiny indivisible particles (atoms)
-atoms of the same element are identical
-the atoms of any one element are different from those of any other element
-atoms of different elements can physically mix together or chemically combine in simple whole-number ratios to form compounds (law of definite/multiple proportions)
-chemical reactions occur when atoms are separated, joined, or rearranged
-atoms of one element are never changed into atoms of another element in a chemical reaction

Question 7

scanning tunneling electron microscope

Answer 7

shows what individual atoms look like

Question 8

3 kinds of subatomic particles

Answer 8

electrons
protons
neutrons

Question 9

JJ Thompson

Answer 9

-performed experiments that involved passing gases through a cathode ray tube
-discovered electrons
-discovered the incorrect structure of the atom
-created the “plum pudding” model

Question 10

cathode ray

Answer 10

-stream of electrons
-glowing beam
-travels from the negative electrode to the positive electrode
-deflected by a magnet/electrically charged plates

Question 11

electrons

Answer 11

-negatively charged subatomic particles
-1/1840 the mass of a proton

Question 12

millikan’s oil drop experiment

Answer 12

-Robert Millikan deduced the charge of a single electron
-measured the strength of the electric field required to halt the free fall of the drops
-determined the radii and density of the drops
-determined the charge of a single electron

Question 13

charge of an electron

Answer 13

-1.60x10^19 C

Question 14

Goldstein

Answer 14

observed the cathode-ray tube and found rays traveled in the opposite direction to the cathode rays and found they were protons

Question 15

protons

Answer 15

positively charged subatomic particles

Question 16

Chadwick

Answer 16

confirmed the existence of neutrons

Question 17

neutrons

Answer 17

-subatomic particles with no charge
-mass equal to a proton

Question 18

Rutherford

Answer 18

-directed a narrow beam of alpha particles at a thin sheet of gold foil
-alpha particles scattered from the gold foil
-concluded the atom is mostly empty and the nucleus

Question 19

nucleus

Answer 19

the tiny central core of an atom composed of protons and neutrons